Biodegradable magnesium (Mg)-based alloys are one of the most promising biomaterials for orthopedic and cardiovascular stent applications. The objective of this proposal is to investigate the effects of Mg and alloying elements commonly used in stent scaffolds on endothelial cells' health. Mg possesses many advantages over conventional biomaterials, such as biodegradability and good biocompatibility. Tailored Mg alloys have the potential for eliminating high rate of late restenosis and thrombogenesis in permanent stent materials. Moreover, some Mg-based stents are currently under clinical trials with encouraging outcomes. However, it still remains as a gap in the current base of our knowledge on how these individual Mg ion and alloying elements affect endothelial cell functions and activities. The central hypothesis of this proposal is that Mg ion and alloying elements will alter the cellular functions and activities of endothelial cells in a concentration dependent manner. Critical endothelial cell endpoints that are needed for a healthy response to alloys including good cell viability and proliferation, unimpaired cell mobility, preserved NO responses, and limited NADPH oxidase or mitochondrial reactive oxygen species (ROS) formation. The elements included in this study are those commonly used in stent applications, namely, Mg, Ca, Zn, Al, Zr, Y, and Gy, Nd, and Gd. Aim 1 is to determine the effects of these individual alloying elements on the viability, proliferation, and ROS and NO release of endothelial cells. Aim 2 is to determine the effects of these individual alloying elements on the cytoskeletal reorganization, mobility, and junctions and barrier function of endothelial cells. Aim 3 is to determine how each of these alloying elements alters the gene expression profile of endothelial cells. Taken together, the proposed study is significant and unique because it will help answer the question what is the maximum amount of these alloying elements should be added into the alloy such that mechanical and corrosion properties are improved while their deleterious effects on endothelial cells are minimal. It will contribute to filling the existing ga in our knowledge about the safety and toxicity of each of these individual elements on endothelial cells, and provide guidance in future design of ideal cardiovascular implants based on these alloys.